The Japanese Invasion of Manchuria began on September 18th 1931. Imperialist Japan took control of Manchuria by February of 1932. Shortly after Japan set up a puppet government by the name of Manchuko.
This invasion immediately followed the Mukden Incident and was lead by the Kwantung Army of the Japanese Empire. In total the annexation of Manchuria took about six months. Manchuria would be under Japan's control for over a decade until the division of the Japanese Empire in 1945.